The level of water hardness, or amount of dissolved solids, in water can have deleterious effects in many systems. The term “dissolved solids” refers to the presence of calcium and magnesium in water. In general, hard water refers to water having a total dissolved solids (TDS) content in excess of about 200 ppm. However, hard water often has a TDS content in excess of about 400 ppm, and even in excess of about 800 ppm. Water having a molar ratio of calcium to magnesium greater than about 1:1 is also considered to be hard. Often, the molar ratio of calcium to magnesium in hard water is about 2:1 or about 3:1. Excess calcium in the water is known to attack other components of the cleaning composition and to precipitate into solution. Although most locations have hard water, water hardness tends to vary from one location to another.
When hard water is used in conjunction with cleaning compositions, hard water can cause precipitation, etching or corrosion of glass, staining of hard surfaces, or stabilization of bacteria. The hard water can cause precipitation of anionic surfactants in the cleaning composition being used, resulting in scaling on the surface being cleaned. For example, when hard water is included as part of the cleaning composition or as the water of dilution used to clean ware, spotting or filming may remain on the surface after cleaning. Exemplary surfaces that may be affected include, for example: glass, metal and plastic.